This invention relates to the recording of signals on a recording medium, such as video signals on a magnetic tape, and more particularly, to such technique which identifies an optimum recording current level such that video signals may be recorded with high signal-to-noise ratios, thereby permitting a wider band of high frequencies to be used while producing video pictures with good quality.
The quality of an information signal that is recorded on a record medium, such as the signal-to-noise (S/N) ratio, often is a function of the current level with which the signal is recorded. This factor is particularly pronounced in the recording of signals on a magnetic record medium, and especially the recording of video signals in slant tracks on a video tape recorder (VTR). Often, the recording current level that may be set by, for example, the recording amplifier, results in different recording characteristics because the properties of the recording transducer, or magnetic head, vary from one device to another. Thus, the setting of a particular current level by a recording amplifier may result in a record signal of optimum parameters when that signal is recorded by one head, but less than optimum parameters when that same signal is recorded by another. To account for such disparities from head to head, it is conventional to rely upon skilled technicians to set the final adjustment in the recording current level, as by setting the gain of the recording amplifier, as the final step in manufacturing a VTR. This labor-intensive procedure is carried out by recording signals with different current levels, or amplifier gain, observing those signals, reproducing those signals, and then measuring the level of the reproduced signals. The recording current level, or gain, of the recording amplifier then is set to the recording current level or gain that had been used to record the signal which the technician observes as having the highest playback level.
This procedure often is inaccurate, is subject to a wide variety of subjectivity by the technician and adds significantly to the overall expense of the VTR. Moreover, the signal level of a signal that is reproduced from a magnetic medium is not dependent solely upon the recording current level that was used during recording. The type and quality of the magnetic medium influences the reproduced signal level so that even if an optimum recording current level is set in the aforementioned manner, that level may not produce optimum results when the VTR is used with a magnetic medium that differs from the medium which was used by the technician.
Although it is possible for the end user of the VTR to carry out the aforementioned procedure of optimizing the recording current level before the VTR is used, it is desirable not to place such a burden, on the user, particularly if the VTR is intended for consumer use. Furthermore, since the VTR may be used with magnetic media of different qualities and types from one recording session to another, thus requiring the optimizing step to be carried out for each magnetic tape that is used, the prospect of having the optimizing step carried out by the VTR user clearly is unattractive.